1. Field of the Invention
The present invention relates to a transmitting apparatus, a transmitting method, a receiving apparatus, a receiving method, and a transmitting and receiving system, and, more particularly to a stream transmitting apparatus, a stream transmitting method, a stream receiving apparatus, a stream receiving method, and a stream transmitting and receiving system for performing program change (tuning operation) at high speed when a streaming broadcast is received.
2. Description of the Related Art
The terrestrial digital broadcasting has started in Japan. As measures for areas having difficulty in viewing programs aiming at spread and promotion of the terrestrial digital broadcasting, besides the broadcasting satellite, retransmission by IP (Internet Protocol) multicast has been examined (see Ministry of Internal Affairs and Communications, Information Communication Council, Second Intermediate Report, [online], 2005/Jul./29, Internet <http://www.soumu.go.jp/s-news/2005/050729—11.html>. When the terrestrial digital broadcasting is retransmitted by the IP multicast, a user receives and views a streaming broadcast using a television receiver and a video recorder in the same manner as viewing the streaming broadcast using a PC (personal computer) under the present situation.
In general, in the streaming broadcast, data is compressed using a compression technique similar to MPEG (Moving Picture Expert Group). Each of screens of a video stream includes screen data compressed in the screen itself (in FIG. 1 and the following explanation, as in MPEG, the screen data is referred to as I picture) and screen data compressed using reference to screens other than the screen and a difference between the screen and the other screens (in FIG. 1 and the following explanation, as in MPEG, the screen data is referred to as P picture and B picture).
When the streaming broadcast is received on a reception side, it is possible to perform decompression processing to decompress the I picture itself into one screen. However, it is difficult to perform decompression processing for the screens other than the I picture when there is no I picture. Thus, in the streaming broadcast, even if reception is started on the reception side at time T1, when a screen other than the I picture is received, for example, when a B picture 21 shown in FIG. 1 is received, it may be impossible to start processing for display until an I picture 24 is received. As a result, display start time is from time T2.
Alternatively, a transmitting apparatus (a server) performs control to start delivery from the I picture (e.g., an I picture 16 in FIG. 1) in response to a delivery request. This makes it unnecessary to wait for reception of the I picture on the reception side.
In the streaming broadcast, video data is transmitted to a receiving apparatus using an IP network. As the IP network, an FTTH (Fiber to The Home) or the like is used up to a home and a facility and a wire LAN (Local Area Network) such as the Ethernet (registered trademark) or a wireless LAN is used in the home and the facility.
The FTTH, the ADSL (Asymmetric Digital Subscriber Line), the Ethernet (registered trademark), and the like are networks of the best-effort type in which a maximum value of communication speed is indicated but is not always guaranteed and speed may suddenly fall due to occurrence of congestion. Therefore, if there is a network of the best-effort type at least in a part of a network between a streaming broadcast delivery server and a reception terminal, communication speed is not guaranteed and temporary fall in the communication speed is inevitable. Thus, in a terminal that receives the streaming broadcast, to prevent a broadcast from being suspended even if communication is interrupted, the broadcast is played after storing (buffering) a fixed quantity of data of a video stream in a storage device or the like (hereinafter referred to as buffer).